Microbial Ecology

, Volume 68, Issue 2, pp 370–378

Minor Changes in Soil Bacterial and Fungal Community Composition Occur in Response to Monsoon Precipitation in a Semiarid Grassland

  • Theresa A. McHugh
  • George W. Koch
  • Egbert Schwartz
Soil Microbiology

DOI: 10.1007/s00248-014-0416-3

Cite this article as:
McHugh, T.A., Koch, G.W. & Schwartz, E. Microb Ecol (2014) 68: 370. doi:10.1007/s00248-014-0416-3


Arizona and New Mexico receive half of their annual precipitation during the summer monsoon season, making this large-scale rain event critical for ecosystem productivity. We used the monsoon rains to explore the responses of soil bacterial and fungal communities to natural moisture pulses in a semiarid grassland. Through 454 pyrosequencing of the 16S rRNA gene and ITS region, we phylogenetically characterized these communities at 22 time points during a summer season. Relative humidity increased before the rains arrived, creating conditions in soil that allowed for the growth of microorganisms. During the course of the study, the relative abundances of most bacterial phyla showed little variation, though some bacterial populations responded immediately to an increase in soil moisture once the monsoon rains arrived. The Firmicutes phylum experienced over a sixfold increase in relative abundance with increasing water availability. Conversely, Actinobacteria, the dominant taxa at our site, were negatively affected by the increase in water availability. No relationship was found between bacterial diversity and soil water potential. Bacterial community structure was unrelated to all environmental variables that we measured, with the exception of a significant relationship with atmospheric relative humidity. Relative abundances of fungal phyla fluctuated more throughout the season than bacterial abundances did. Variation in fungal community structure was unrelated to soil water potential and to most environmental variables. However, ordination analysis showed a distinct fungal community structure late in the season, probably due to plant senescence.

Supplementary material

248_2014_416_MOESM1_ESM.pptx (617 kb)
Fig. S1Visual observations of the grassland before (Julian Day 174), during (Julian Day 201), and after (Julian Day 224) monsoon rains (PPTX 616 kb)
248_2014_416_MOESM2_ESM.pptx (40 kb)
Fig. S2A moisture release curve for our clay soil (PPTX 39 kb)
248_2014_416_MOESM3_ESM.pptx (43 kb)
Fig. S3Nitrate and ammonium concentrations during the study period.Error bars are standard error for means (n = 5) (PPTX 43 kb)

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Theresa A. McHugh
    • 1
  • George W. Koch
    • 1
  • Egbert Schwartz
    • 1
  1. 1.Department of Biological SciencesNorthern Arizona UniversityFlagstaffUSA

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